BUENOS AIRES (Reuters) - Candidates sponsored by Argentine opposition leader Sergio Massa won the House of Deputies' midterm election by a 10-percentage-point margin on Sunday in the key province of Buenos Aires, according to an exit poll announced on television channel TN.
Opposition parties ran against President Cristina Fernandez's FPV coalition in the mid-term. About the size of Italy, Buenos Aires province is home to 40 percent of Argentina's population and most of the country's agricultural output.
Massa, the mayor of the affluent Buenos Aires town of Tigre, headed his own list of candidates for Congress and is seen as a possible, business-friendly presidential contender in 2015.
(Reporting by Hugh Bronstein; Editing by Sandra Maler)